*>EPA

United States
Environmental Protection
Agency

Environmental Monitoring
Systems Laboratory
P.O. Box 93478

July 1991

Las Vegas NIV 89193-3478 • ^ ^ ^

OFFICE OF RESEARCH AND DEVELOPMENT	

Continuous
Monitoring with
Purge-and-Trap
Gas

Chromatography

DGY5

-O-

TECHNOLOGY SUPPORT PROJECT

Final
Report



INTRODUCTION

Preliminary site assessment
and monitoring ot remedia-
tion ettorts rely upon timely
and accurate intormation.
Various methods exist tor the
continuous monitoring ot
water and air samples, their
value lies in the elimination ot
labor-intensive sample
collection, handling, and
analytical procedures. The
generation ot real-time data
permits treatment systems to
operate in a true process
control mode. Additionally,
data quality may be better
since samples are never
subjected to the packaging
and transport needed tor
conventional laboratory
analysis.

The Environmental Monitor-
ing Systems Laboratory - Las
Vegas (EMSL-LV) is inter-
ested in the application ot
continuous monitoring
technologies that will reduce

the time-in-tield tor environ-
mental scientists working at
Supertund and RCRA sites.
A system developed by
Analytic and Remedial
Technology, Inc. was evalu-
ated tor the on-line monitoring
ot volatile organic compounds
(VOCs) in a ground-water
treatment process. This
monitoring system, Automated
Volatile Organic Analytical
System (AVOAS), consists ot
a sampling manitold, a purge-
and-trap unit coupled to a gas
chromatograph (GC)
equipped with an electrolytic
conductivity (or Hall) detector
and a computer system. The
innovative components ot this
system are:

(1) the sampling manitold,
which allows tor direct,
on-line intake ot samples
trom different collection
points or treatment
streams.

(2)	the injector, which allows
direct injection of the
sample into the GC
without the handling and
prepa ation steps often
associated with VOC loss
due to volatilization.

(3)	the computer software
that is customized for the
analysis system.

The AVOAS was tested at a
Superfund site in Region 1
under the Superfund Innova-
tive Technology Evaluation
(SITE) program. Under the
conditions of this study, the
EMSL-LV found this system
to be reliable and easy to
use. Comparisons of data
from the AVOAS study with
standard analytical laboratory
results from sample splits
indicate a strong correlation.
The AVOAS results were
consistently higher, perhaps
reflecting differences due to
sample loss during transport.

DEMONSTRATION

The evaluation was con-
ducted at the Wells G&H Site
in Woburn, MA, U.S. EPA
Region 1. Ground water at
the site is known to be
contaminated with VOCs.
Remedial action required
treatment of the ground water
to remove the VOC contami-
nation. As a result, a pilot-

scale operation of a ground-
water extraction and treat-
ment system was conducted
to evaluate the relative merits
of three treatment processes:
an ultraviolet/chemical
oxidation process, a carbon
adsorption process, and an
experimental dehalogenation
process.

Six sampling points in the
"treatment train" were se-
lected to monitor the effi-
ciency of the individual
methods for reducing VOC
content. These discrete
samples were sent off-site for
standard analyses using a
purge and trap GC/MS

(Continued)

0697? X 31

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DEMONSTRATION
(Continued)

method. This treatment
study presented an excellent
opportunity to demonstrate
and evaluate the AVOAS as
an application of the prin-
ciples of process analytical
chemistry during a remedia-
tion activity. The AVOAS

was programmed to collect
and analyze samples at six
collection points. In addition
to the GC/MS samples,
matching samples were
taken and shipped to the
EMSL-LV for analysis by
EPA GC Method 502.2. The

AVOAS GC analysis is similar
to Method 502.2, making
direct comparison allowable.
A variety of QA/QC samples
were also analyzed under
each protocol, consistent with
the requirements of the study
design.

ADVANTAGES AND
LIMITATIONS

The use of continuous
monitoring devices holds
great promise for enhancing
the characterization and
remediation activities at a
hazardous waste site. The
increasing number of these
devices coming into the
environmental market puts a
burden of evaluation upon
both manufacturer and
consumer. There is no gain
in sacrificing data reliability
for ease of use. The EMSL-
LV will continue to evaluate
the performance of demon-
strated technologies, like the
AVOAS, for applications
where a need is indicated.

Advantages

Limitations

Eliminates problems
associated with
standard VOC
sampling and
'ransport

Allows selection of
sampling point,
frequency, intervals

Reduces labor costs

Provides real-time,
in-situ data

Minimizes exposure
of field personnel

Initial hardware cost

Problems associated
with long-term operation
need to be identified

Availability of equipment

Application to other
situations must be
explored

REFERENCES

Volatile Organic Compounds in Water by Purge and Trap Capillary Column Gas Chromatogra-
phy with Photoionization and Electrolytic Conductivity Detectors in Series, Method 502.2, U.S.
EPA, Cincinnati, 1986.

Methods for the Determination of Organic Compounds in Water, U.S. EPA, Office of Research
and Development, Cincinnati, 1986.

FOR FURTHER INFORMATION

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For more information about this study and how continuous monitoring of ground water may
help you, contact:

Dr. Stephen Billets

Quality Assurance and Methods Development Branch
Environmental Monitoring Systems Laboratory
Las Vegas, NV

(702) 798-2232, (FTS) 545-2232

For information about the Technology Support Center at EMSL-LV, contact:

Mr. Ken Brown, Manager

Technology Support Center

U.S. Environmental Protection Agency

Environmental Monitoring Systems Laboratory

P.O. Box 93478

Las Vegas, NV 89193-3478

(702) 798-2270

The Technology Support Center fact sheet series is developed and written by
Clare L. Gerlach, Lockheed Engineering & Sciences Company, Las Vegas.

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